Optimizing Pump Selection for Energy Efficiency Across Multiple Operating Conditions Using True Weighted Efficiency (TWE)

Energy efficiency is emphasized more actively across the pump industry. Legislation in the European Union and in the United States utilize new energy efficiency ranking metrics, but neither of these methods are conveniently applied to customer specified load conditions. True Weighted Efficiency, or TWE, is introduced as a general-purpose, universal pump efficiency metric for pumps operating under multiple operating conditions. The TWE is derived accurately from first principles, using generalized load profiles that include control curves, multiple discrete operating points based on those control curves, and the time of operation at each operating point. A pump selection/optimization program is used to numerically demonstrate the TWE method. Various examples are presented, contrasting candidate pumps based on three different optimization strategies. The study reveals that the pump with the best design point efficiency may not be the best choice from a TWE or an evaluated cost perspective. This method is applicable to rotodynamic or positive displacement pumps operating at fixed or variable speed, on/off operation, throttle control, or by-pass control. and other turbomachinery as well. The TWE methodology, when combined with a pump selection/optimization program, will help practitioners design systems that reduce energy consumption for new or reconfigured pump applications.

Small Wind Turbine Emulator Based on Lambda-Cp Curves Obtained under Real Operating Conditions

This paper proposes a new on-site technique for the experimental characterization of small wind systems by emulating the behavior of a wind tunnel facility. Due to the high cost and complexity of these facilities, many manufacturers of small wind systems do not have a well knowledge of the characteristic λ - C p curve of their turbines. Therefore, power electronics converters connected to the wind generator are usually programmed with speed/power control curves that do not optimize the power generation. The characteristic λ - C p curves obtained through the proposed method will help manufacturers to obtain optimized speed/power control curves. In addition, a low cost small wind emulator has been designed. Programmed with the experimental λ - C p curve, it can validate, improve, and develop new control algorithms to maximize the energy generation. The emulator is completed with a new graphic user interface that monitors in real time both the value of the λ - C p coordinate and the operating point on the 3D working surface generated with the characteristic λ - C p curve obtained from the real small wind system. The proposed method has been applied to a small wind turbine commercial model. The experimental results demonstrate that the point of operation obtained with the emulator is always located on the 3D surface, at the same coordinates (rotor speed/wind speed/power) as the ones obtained experimentally, validating the designed emulator.

Numerical Investigation of a Process Control for the Roller Levelling Process Based on a Force Measurement

When processing conventional semi-finished metal strips, distinctive changes in the material properties along the strip length are unavoidable. The roller levelling process is sensitive to changes of those strip characteristics. Thus, a process control allowing for an online adaption of the roller levelling machine according to the actual strip characteristics is highly desirable. In order to enable a precise process layout, the calculation by the Finite Element Method (FEM) provides a suited strategy. Furthermore, the coupling of user-subroutines to an FE code offers the possibility to implement and test respective control strategies. This work proposes a control strategy that is based on a force measurement in the first load triangle of a levelling machine. A first FE model including a feedback control is used to calculate the dependence between the force in the first load triangle and the roll intermesh in the last load triangle leading to a flat sheet. The results are transferred to meta models – so called control curves – that give a direct relationship between the measured force and the roll intermesh. Within a second FE setup a feed-forward control based on these control curves is implemented and the proposed control strategy is investigated for varying yield strengths along the strip length. Thus, the time consuming FE simulations that are necessary to obtain the control curves are decoupled from the actual levelling process. According to the obtained results, the introduced approach is able to improve the sheet flatness for thin sheets when a change in the material properties occurs.

Parametric Generation of Planing Hulls with NURBS Surfaces

This article presents a mathematical method for producing hard-chine ship hulls based on a set of numerical parameters that are directly related to the geometric features of the hull and uniquely define a hull form for this type of ship. The term planing hull is used generically to describe the majority of hard-chine boats being built today. This article is focused on unstepped, single-chine hulls. B-spline curves and surfaces were combined with constraints on the significant ship curves to produce the final hull design. The hard-chine hull geometry was modeled by decomposing the surface geometry into boundary curves, which were defined by design constraints or parameters. In planing hull design, these control curves are the center, chine, and sheer lines as well as their geometric features including position, slope, and, in the case of the chine, enclosed area and centroid. These geometric parameters have physical, hydrodynamic, and stability implications from the design point of view. The proposed method uses two-dimensional orthogonal projections of the control curves and then produces three-dimensional (3-D) definitions using B-spline fitting of the 3-D data points. The fitting considers maximum deviation from the curve to the data points and is based on an original selection of the parameterization. A net of B-spline curves (stations) is then created to match the previously defined 3-D boundaries. A final set of lofting surfaces of the previous B-spline curves produces the hull surface.

A new six-parallel-legged walking robot for drilling holes on the fuselage

In this paper, a new kind of six-parallel-legged robot is presented. It is designed for drilling holes on the aircraft surface. Each leg of the robot is a 3-DOF parallel mechanism with three chains: 1UP and 2UPS. The three prismatic joints are active joints and can be controlled either by position or by force. First, the task process and the gait plan are discussed and then, according to the requirement, the control method is introduced. After that, the mechanism topology patterns under different working conditions are studied and the control mode of each motor is determined. Then the kinematical model is built up, based on which the position control curves can be obtained. The simulation result shows that the robot can walk pretty well on the fuselage surface and that the actuation forces are quite smooth. Furthermore, the first prototype has been manufactured and some experiments such as walking and manipulation have been done.